Since I use Latest as my main method for browsing, I’ve taken to using open in new tab for all posts, to avoid a refresh that will drop the whispers. But it seems to me that if the bump works once, it’s probably a bug that it doesn’t stay there? I’m not sure why you’d bump it once and then intentionally drop it.
As far as I’m concerned, that’s the opposite of a solution for me – I always want to see new whispers bump the topics. Even if someone has said something privately, they’ve still said something and I want to know about it.
I know it’s not the same as seeing them directly in your topic list, but maybe it helps to put a link to that search in a custom sidebar section so you can easily take a look.
In addition to requiring extra steps, the bigger problem there is that sort by is sticky, i.e. using that search to check whispers sets my search to always sort by latest. In fact, I’ve always hated the sticky sort order and I want it to default to relevance every time.